Resistance to the antiretroviral drug tenofovir is “surprisingly and worryingly common”, particularly in sub-Saharan Africa, researchers warned today.
Drug resistance usually occurs when a patient does not take their medication regularly and when treatment is interrupted.
Because supplies are often limited in many parts of Sub-Saharan Africa, it is not unusual for patients to receive treatment until they have advanced HIV disease.
But once a patient’s virus becomes resistant to first-line drugs, the next stage is expensive second-line treatment with greater side effects and many rural patients do not have access to this type of medication.
Scientists at Stanford University and the London School of Hygiene and Tropical Medicine, found tenofovir-resistant strains in 60% of patients in sub-Saharan Africa compared with 20% of patients in Europe.
A study, published last night (28 January, 2016), also revealed that about two thirds of patients with tenofovir-resistant strains had also become resistant to both other drugs in their regimen.
Writing in the Lancet Infectious Diseases, lead author Dr Ravi Gupta, UCL Infection & Immunity, said the study suggests that in Sub-Saharan Africa, up to 15% of HIV patients treated with tenofovir-based drug combinations will develop resistance in the first year of treatment alone.
Resistant strains could be passed on to other individuals, becoming more widespread and potentially compromising global HIV control strategies.
“Tenofovir is a critical part of our armamentarium against HIV, so it is extremely concerning to see such a high level of resistance to this drug,” he said.
“It is a very potent drug with few side-effects, and there aren’t any good alternatives that can be deployed using a public health approach. Tenofovir is used not only to treat HIV but also to prevent it in high-risk groups, so we urgently need to do more to combat the problem of emerging resistance.
“If resistant strains of HIV were significantly less effective at spreading in people, we would expect to see lower levels of the virus in patients with the resistant strain.
“However, we found that virus levels were no lower in individuals with the resistant strain and were high enough to be fully infectious. We certainly cannot dismiss the possibility that resistant strains can spread between people and should not be complacent. We are now conducting further studies to get a more detailed picture of how tenofovir resistant viruses develop and spread.”
The study examined 1,926 HIV patients across the world who, despite being prescribed antiretrovirals, had uncontrolled HIV.
Those whose immune systems were already compromised when they started treatment were 50% more likely to develop tenofovir resistance, as were patients on certain other antiretroviral drugs combined with tenofovir.
Co-author Professor Robert Shafer, of the Stanford University School of Medicine, added: “This study highlights the need for efforts to ensure that the regimens used to treat HIV retain their effectiveness as long as possible.”
Gregson et al, Global epidemiology of drug resistance following failure of WHO recommended first line regimens for adult HIV-1 infection – a multi-centre retrospective cohort study Lancet Infectious Diseases 29 January 2016
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